Individually, he has won medals at the Central American and Caribbean Championships, taking the 400 m silver medal in 2008 and the 200 m gold in 2011. His personal bests are 20.16 seconds for the 200 m and 45.06 for the 400 m (the former being the Bahamian record mark).
In 2004 he began studying economics at Texas Tech University and started competing for the Texas Tech Red Raiders under coach Wes Kittley. In the 2005 indoor track and field season he was runner-up at the Big 12 Conference meet in the 400 m and 4 × 400 m relay. He earned All-American honours by reaching the NCAA indoor relay final, then achieved the same feat in the outdoor season. The 2006 indoor season was his last at Texas Tech: he set a 200 m personal best of 21.34 seconds and again reached the NCAA relay final.[2]
He reached the senior international level at the 2007 World Championships and became a fixture in the Bahamian national team from then onwards. He ran in the heats, both individually and in the relay, at the 2008 IAAF World Indoor Championships,[5] then won two silver medals in the events at the 2008 Central American and Caribbean Championships.[6] At the 2008 Summer Olympics he reached the semi-finals of the 400 m and took the relay silver medal with a time of 2:58.03 minutes.
He opened his 2012 season in strong form. Competing on the Brazilian Athletics Tour, he ran a Bahamian record of 20.16 seconds for the 200 m and set a personal best in the 400 m with a run 45.06 seconds. He also equalled his 100 metres best with a time of 10.30 seconds.[9] He also won gold at the 2012 London Olympics with the Bahamas 4 × 400 m team beating medal favorites USA with a national record.
At the 2016 Summer Olympics, Mathieu and the Bahamian team would win the bronze medal in the 4 × 400 m relay. Another former Texas Tech athlete, Gil Roberts, was a member of the gold medal-winning USA team.[11][12][13]
Retirement
Mathieu retired after the 2021 Outdoor season with his last race being run on June 5, 2021 at the North American, Central American and Caribbean (NACAC) New Life Invitational Track and Field Meet in Miramar, Florida.. He ran on a leg of the Bahamian 4x400 Metres Relay in a time of 3:03.51. The team was attempting to qualify for the 2020 Olympic Games.[14]
Mathieu now lives in Orlando, Florida with his wife and two sons. He coaches youth basketball for the Jr. Magic Warriors, along with owning a speed training camp company to help build speed for different sports.[15]